Franck-Condon and Jahn-Teller effects in the E '(1) state of (CO)(2)(-)(5) molecule. Resonance and preresonance Raman study in terms of time-dependent density functional theory: New insight into an old story

摘要

Franck-Condon and Jahn-Teller effects in the E-1(') state of the croconate dianion are studied in terms of time-dependent density functional theory (TD-DFT) at the B3LYP/aug-cc-pVDZ and BP86/aug-cc-pVDZ levels. The results of these treatments are then used to discuss the empirical absorption, preresonance, and resonance Raman spectra associated with A(1)(') -> E-1(') transition in the croconate dianion. In agreement with the experiment, the computations done at the B3LYP/aug-cc-pVDZ level of Ad approximation predict substantial Jahn-Teller and Franck-Condon activities of v(2) (a(1)') 607 cm(-1) (ring-breathing) and v(11) (e(2)(')) = 526 cm(-1) (ring-bending) modes in the lowest-energy E-1(') state of the croconate ion. The activities of the other e(2)(')- and a(1)(')-symmetry modes were found to be quite modest. It is shown that the sizable activities of v(2) (a(1)(')) and v(11) (e(2)(')) modes lead to Bactrian-like structure in the absorption corresponding to the 2 A(1)(') -> E-1('), transition. Taking into account the consistencies between the electronic absorption and Raman experiments, we can convincingly argue that the double-band shape experimentally observed in the absorption of the croconate dianion cannot be attributed to solute-solvent interactions, as was recently proposed. (c) 2005 Wiley Periodicals, Inc.